Research Paper

The migraine brain in transition: girls vs boys Vanda Fariaa,b,*, Nathalie Erpeldinga, Alyssa Lebela,c, Adriana Johnsona, Robert Wolffd, Damien Faire,f, Rami Bursteing, Lino Becerraa, David Borsooka,c

Abstract The prevalence of migraine has an exponential trajectory that is most obvious in young females between puberty and early adulthood. Adult females are affected twice as much as males. During development, hormonal changes may act on predetermined brain circuits, increasing the probability of migraine. However, little is known about the pediatric migraine brain and migraine evolution. Using magnetic resonance imaging, we evaluated 28 children with migraine (14 females and 14 males) and 28 sexmatched healthy controls to determine differences in brain structure and function between (1) females and males with migraine and (2) females and males with migraine during earlier (10-11 years) vs later (14-16 years) developmental stages compared with matched healthy controls. Compared with males, females had more gray matter in the primary somatosensory cortex (S1), supplementary motor area, precuneus, basal ganglia, and amygdala, as well as greater precuneus resting state functional connectivity to the thalamus, amygdala, and basal ganglia and greater amygdala resting state functional connectivity to the thalamus, anterior midcingulate cortex, and supplementary motor area. Moreover, older females with migraine had more gray matter in the S1, amygdala, and caudate compared to older males with migraine and matched healthy controls. This is the first study showing sex and developmental differences in pediatric migraineurs in brain regions associated with sensory, motor, and affective functions, providing insight into the neural mechanisms underlying distinct migraine sex phenotypes and their evolution that could result in important clinical implications increasing treatment effectiveness. Keywords: Children, MRI, Migraine, Development, Puberty, Sex differences

1. Introduction Considered by the World Health Organization to be one of the leading causes of disability worldwide,9 migraine is a neurological disorder, characterized by intermittent headaches, that commonly starts in early childhood, increases in prevalence with puberty, and continues throughout adulthood.19 Neuroimaging studies have led to remarkable insight in the description of migraine pathophysiology and in the identification of structural and functional changes associated with this debilitating disorder by contrasting adult migraineurs with adult healthy controls.15,51

Sponsorships or competing interests that may be relevant to content are disclosed at the end of this article. a

Center for Pain and the Brain, Department of Anesthesiology, Perioperative and Pain Medicine, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA, b Department of Psychology, Uppsala University, Uppsala, Sweden, c Chronic Headache Program, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA, d Department of Neurology, Boston Children’s Hospital, Harvard Medical School, Boston, MA, USA, Departments of e Behavioral Neuroscience and, f Psychiatry, School of Medicine, Oregon Health and Science University, Portland, OR, USA, g Department of Anesthesia and Critical Care, Beth Israel Deaconess Medical Center, Harvard Medical School, Boston, MA, USA *Corresponding author. Address: Center for Pain and the Brain, c/o PAIN Group, Boston Children’s Hospital, Harvard Medical School, Boston, MA 02453, USA. Tel.: 781-216-1199; fax: 781-216-1983. E-mail address: vanda.rochafaria@childrens. harvard.edu (V. Faria). Supplemental digital content is available for this article. Direct URL citations appear in the printed text and are provided in the HTML and PDF versions of this article on the journal’s Web site (www.painjournalonline.com). PAIN 156 (2015) 2212–2221 © 2015 International Association for the Study of Pain http://dx.doi.org/10.1097/j.pain.0000000000000292

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Importantly, epidemiological evidence shows that in adults, migraine affects twice as many females as males.53 Adult females report more frequent, longer lasting, and more painful headaches compared with males.19 Nevertheless, only a few studies29,34 have examined the underlying neural differences between females and males with migraine. In a recent study from our group, we found that compared with male migraineurs, female migraineurs exhibited unique neural changes in interoceptive, emotional, and associative processing regions such as the insula, amygdala, and precuneus (PCu),34 supporting the notion of a migraine sex phenotype. It is well known that puberty influences the female and male brain differently.8 When it comes to migraine, puberty is also a time of transition. Epidemiological studies suggest that the phenotypical expression of migraine is not consistent across ages.28,38,52 Changes in the endocrine milieu during development may contribute to the increased sex differences observed in migraine as a result of their influence on brain function.5,45 Notably, although until the age of 9, there are no significant differences in migraine prevalence between males and females, after the age of 10, the disparity emerges, peaking in the third decade and dissipating during the sixth decade.19 Although the complex pathophysiology of migraine suggests the involvement of a multitude of factors, the high prevalence of migraine in females of reproductive age and the lower prevalence of migraine in females before puberty and post-menopause indicate that hormonal factors may play a key role in migraine.5,13 In addition, epigenetic factors,17 differential responses to stress, and pain perception have been proposed as potential contributing factors.1,22 To date, however, no studies on brain structure and function have been conducted in children to examine migraine-related sex differences. PAIN®

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Accordingly, we investigated structural and functional neural differences in children with migraine compared with healthy sexand age-matched controls. Specifically, our aims were to determine whether (1) males and females with migraine exhibit differences in brain structure and function compared with healthy controls, (2) structural and functional neural changes show differences at an earlier (ie, 10-11 years) vs later age (ie, 14-16 years), and (3) structural and functional changes overlap with previously observed sex differences in adult migraineurs.34 The outcome of this study may contribute to a better understanding of the neural mechanisms underlying distinct migraine sex phenotypes and their evolution, resulting in potentially important implications for treatment effectiveness.

2. Materials and methods 2.1. Subjects The study was approved by the Institutional Review Board at Boston Children’s Hospital. The protocol conformed with the ethical principles developed by the Declaration of Helsinki11 for conducting research involving human subjects and with the International Association for the Study of Pain criteria for performing human pain investigations.14 Patients and parents were consented for the study. Parents were present during the study visits. A total of 56 subjects were recruited for the study. Twenty-eight patients, 14 females (mean age 6 SD 5 13.1 6 2.7 years) and 14 males (mean age 5 12.8 6 2.7 years), with migraine were recruited from the neurology and headache departments at Boston Children’s Hospital. Twenty-eight sex- and age-matched healthy controls were recruited through advertisements at Boston Children’s Hospital and in the greater Boston area (Fig. 1). Patients were included in the study if they (1) had a diagnosis of migraine with or without aura, (2) were right-handed, and (3) were able to participate during the interictal period. They were excluded if they had (1) significant medical problems (eg, uncontrollable asthma and seizures, cardiac diseases, severe psychiatric disorders, and neurological disorders other than migraine); (2) pregnancy; (3) claustrophobia; (4) metallic implants and/or devices; and (5) weight .285 pounds, which corresponds to the weight limit of the magnetic resonance imaging (MRI) table.

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For each patient, the migraine diagnosis was made in accordance with the International Classification of Headache Disorders guidelines, stating that at least 5 migraine attacks of at least 1 hour in duration need to have occurred to reliably diagnose migraine in children. This is contrary to diagnosis in adults with migraine, as migraine episodes should typically last 4 to 72 hours when left untreated; however, each attack needs to last only 1 hour to qualify in children. Study visits included a neurological examination with a study physician and MRI. Medication use and migraine characteristics are listed in Table 1. 2.2. Magnetic resonance imaging acquisition Subjects underwent MRI on a 3 T scanner (Siemens Medical Solutions, Erlangen, Germany) equipped with a 32-channel head coil. For each participant, a 3-dimensional T1-weighted scan using a magnetization-prepared rapid acquisition gradient echo sequence (160 slices; TR 5 1410 milliseconds; TE 5 2.27 milliseconds; TI 5 800 milliseconds; 256 3 256 matrix; FOV 5 200 mm; 0.8 3 0.8 3 1.0 mm voxels) was acquired. We also collected a T2*-weighted echoplanar pulse imaging (EPI) scan (41 slices; TR 5 3000 milliseconds; TE 5 35 milliseconds; 64 3 64 matrix; FOV 5 1680 mm; 3.75 3 3.75 3 3.5 mm voxels). For the EPI scan, subjects were instructed to relax with their eyes open looking at a blank screen. 2.3. Magnetic resonance imaging preprocessing and data analysis 2.3.1. Cortical thickness Cortical thickness preprocessing and analysis steps were performed using FreeSurfer (http://surfer.nmr.mgh.harvard.edu). Magnetization-prepared rapid acquisition gradient echo scans were preprocessed performing (1) intensity normalization, (2) skull stripping, (3) Talairach transformation, (4) hemispheric separation, (5) tissue segmentation, (6) identification of white surface and pial surface, (7) cortical parcellation, and (8) registration to the average surface map. Scans were smoothed using a 5-mm full-width halfmaximum (FWHM) Gaussian smoothing kernel.

Figure 1. Flowchart of study subjects. Twenty-eight children with migraine (14 females, 7 between 10 and 11 years and 7 between 15 and 16 years, and 14 males, 7 between 10 and 11 years and 7 between 15 and 16 years) and 28 sex- and age-matched healthy control children were enrolled this study. All participants underwent magnetic resonance imaging. Statistical analyses were based on data contrasting females (n 5 14) and males (n 5 14) and females vs males at early puberty vs midpuberty (n 5 7).

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Table 1

Patient demographics. Age

Sex Time with Diagnosis migraine, y

16 16 16

F F F

11 13 3.5

15 16 10 10 11 10 15 16 16 14 11 10 10 15 10 10 15 11 15 10 11 11 11 16 16

F M M F F F M F F M M M M M F M M F F M M F F M M

4 12 2 1 2.5 5 5 4 4 1 4 2 5 1 2 0.5 4 7.5 8 8 4 4 9 2 2

Mg with aura Mg with aura Mg with aura and without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg without aura Mg with aura Mg without aura Mg without aura Mg without aura Mg with and without aura Mg without aura Mg with aura Mg without aura Mg with and without aura Mg with aura Mg with aura Mg with aura

Frequency Duration, h (per month)

Medication Abortive Preventive Pain

Pain intensity * Pain (0-10) unpleasantness * (0-10)

2 1 1.5

6 4.5 24

X X X

X X X

— — —

10 8.5 7.5

10 8 7.5

12 4 2 30 1 30 12 6 6 10 4 2.5 4 0.25 8 3.5 5 0.5 5 3.5 8 8 1.5 3.5 3

Md 7.5 10 24 72 2.5 4 24 4.5 1.75 3 13.5 4.5 1.5 2.5 1.5 1 Md 24 1.5 8 2 1.5 24 5

X X — X X — X X — — — — X X — — — — X — — — X — X

— X — — X X X X X — — — X — — — X — X — X — — — —

— — X — — X X X X X — X X X X X X X X X X X — X X

6.5 4 5 6 7 10 6.5 9.5 8 6 7 9 9 8 7 7 5 Md 7.5 3 5.5 6 7 8.5 7.5

10 6.5 7 6 6 3 7 10 8 6 8 8 8 8 8 8 4 Md 7.5 7 6 5 7 8.5 9

* 0, no pain at all; 10, worst pain imaginable. Migraine characteristics collected at the time of the study. F, female; M, male; Mg, migraine; Md, missing data.

Cortical thickness analysis was performed using a mask including brain areas consistently implicated in migraine,5,6,15,31,34,51 such as the primary sensory cortex (S1), primary motor cortex (M1), insula, PCu, dorsolateral prefrontal cortex, frontal pole, and temporal pole. The total intracranial volume was entered as a variable of no interest to control for potential differences in subjects’ head size. Results were corrected for multiple comparisons based on Monte Carlo permutations with 5000 iterations using AlphaSim (http://afni. nimh.nih.gov/afni/doc/manual/AlphaSim). Using an image-wide threshold of P , 0.01 and a Bonferroni-corrected P , 0.025 (to correct for each hemisphere), AlphaSim simulations revealed that 75 contiguous vertices for the left hemisphere and 74 contiguous vertices for the right hemisphere were required for clusters to be significant. 2.3.2. Subcortical volume Subcortical gray matter (GM) volume analysis was performed with voxel-based morphometry (VBM) using FSL-VBM.16 Magnetization-prepared rapid acquisition gradient echo scans underwent (1) brain extraction, (2) tissue-type segmentation into GM, white matter (WM), and cerebrospinal fluid (CSF), (3) nonlinear registration of GM partial volume maps to MNI152 standard space, (4) creation of a study-specific GM template, (5) nonlinear registration of GM images to the study-specific GM template, and (6) local expansion or contraction modulation correction (ie, by dividing them by the Jacobian of the warp field).

Finally, the modulated registered GM images were smoothed with a FWHM kernel of a sigma of 3. Voxel-based morphometry analysis was performed using a mask including subcortical regions previously involved in migraine,23,32,34,51 such as the thalamus, caudate, putamen, pallidum, hippocampus, nucleus accumbens, amygdala, hypothalamus, and periaqueductal gray. This mask was created using the Harvard–Oxford Subcortical Structural Atlas in FSL (http:// www.cma.mgh.harvard.edu/). Results were corrected for multiple comparisons with Monte Carlo simulations in AlphaSim using an image-wide threshold of P , 0.01 and an alpha of P , 0.05 with 5000 iterations. Clusters with 34 contiguous voxels were required to be significant. 2.3.3. Seed-based resting state functional connectivity Seed-based resting state functional connectivity (rsFC) was performed using FEAT in FSL. Echoplanar pulse imaging scans were preprocessed by performing (1) 0.01 Hz filtering, (2) removal of first 4 volumes, (3) brain extraction, (4) motion correction, (5) linear registration to anatomical space, and (6) nonlinear registration to MNI152 standard space. Scans were smoothed using a 5-mm FWHM kernel. Subject scans were excluded if motion .3 mm was detected. The 6 motion parameters (ie, 3 rotation and 3 translation) that were generated from motion correction were entered as variables of no interest. Additionally, WM and CSF were included as variables of no interest into our model. To do so, the segmented

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Table 2

Cortical GM thickness in females and males with migraine and healthy controls. Contrasts/cortical brain regions Females (Mg . Hc) . males (Mg . Hc) L primary somatosensory cortex R SMA R PCu Males (Mg . Hc) . females (Mg . Hc) NS

MNI coordinates x

y

z

260 31 13

212 27 260

29 52 32

No. of vertices

t score

180 124 76

24.10 23.59 23.60

GM, gray matter; Hc, healthy controls; L, left; Mg, migraineurs; NS, not significant; PCu, precuneus; R, right; SMA, supplementary motor area.

magnetization-prepared rapid acquisition gradient echo WM and CSF maps were registered to each subject’s functional space, thresholded at 80%, and binarized. Average time courses for each map were extracted and included into the first-level analysis as variables of no interest. A data-driven approach was used to perform rsFC. Specifically, we explored whether females with migraine exhibit alterations in rsFC in regions implicated in emotional and cognitive aspects of pain processing with significant GM differences compared with males with migraine. Thus, we performed rsFC from the left and right amygdala, as well as from the right PCu. To do so, we placed 5-mm spheres around each peak coordinate. We used a peak coordinate approach rather than the entire cluster to prevent our findings to be tampered by rsFC from subregions of the PCu and amygdala. Spheres were then registered to each subject’s functional space. Finally, average time courses were extracted from the preprocessed EPI scans and entered into our first-level analysis. Higher-level group analyses were conducted in FEAT using FLAME to investigate amygdala and PCu rsFC differences between patients and controls and between females and males. Results were corrected for multiple comparisons using cluster correction with z . 2.3 and P , 0.05.

3. Results 3.1. Descriptive findings All children with migraine were sex- and age-matched with healthy control children. There were no significant sex differences between patients regarding time with migraine (females mean

duration 6 SD 5 5.6 6 3.5 years; males mean duration 5 3.8 6 3.1 years; t(df) 5 2.05(26), P 5 0.15), migraine frequency (females mean frequency 5 8 6 9.9 migraines per month; males mean frequency 5 4.7 6 3.2 migraines per month; t(df) 5 2.12(16), P 5 0.24), or pain unpleasantness (females mean pain unpleasantness 5 7.3 6 2.1; males mean pain unpleasantness 5 7.2 6 1.3; t(df) 5 2.08(20), P 5 0.80). However, there is a tendency suggesting underlying differences when it comes to migraine duration (females mean duration 5 15.9 6 20.3 hours; males mean duration 5 6.2 6 6.3 hours; t(df) 5 2.16(13), P 5 0.13) and pain intensity (females pain intensity 5 7.7 6 1.4; males pain intensity 5 6.5 6 1.9; t(df) 5 2.06(24), P 5 0.06). Notably, females display higher values in both migraine duration and pain intensity compared with males with migraine (Table 1). 3.2. Sex differences in migraine 3.2.1. Structural findings Contrasting sex-related cortical GM differences between patients and controls revealed a sex-by-disease interaction, indicating that females with migraine have significant GM thickening in the left S1, right supplementary motor area (SMA), and right PCu compared with males with migraine and healthy controls (Table 2 and Fig. 2A). Structural brain differences between patients and healthy controls within sex are reported in Supplementary Table 1 (available online as Supplemental Digital Content at http://links. lww.com/PAIN/A125). Our VBM analysis revealed that, when comparing sex-related GM volume changes between patients and controls, female patients had significantly more GM in the right caudate, bilateral

Figure 2. Sex-related structural brain differences between patients with migraine (Mg) and healthy controls (Hc). (A) Females with migraine (shown in pink) had gray matter thickening in the left primary somatosensory cortex (S1), right supplementary motor area, and right precuneus compared with males with migraine and healthy controls. (B) Females with migraine (shown in pink) had more gray matter in the right caudate (Cau), bilateral amygdala (Amy), and right pallidum (Pal) compared with males with migraine and healthy controls.

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Table 3

Subcortical GM volume in females and males with migraine and healthy controls. Contrasts/subcortical brain regions Females (Mg . Hc) . males (Mg . Hc) R caudate R amygdala L amygdala R pallidum Males (Mg . Hc) . females (Mg . Hc) NS

MNI coordinates x

y

z

14 32 228 12

2 26 22 24

24 220 228 26

No. of voxels

t score

471 58 55 36

2.6 3.13 2.7 2.68

GM, gray matter; Hc, healthy controls; L, left; Mg, migraineurs; NS, not significant; R, right.

amygdala and the bilateral thalamus, right SMA, and bilateral anterior midcingulate cortex (aMCC) compared with male patients and healthy control subjects (ie, significant sex-bydisease interaction) (Table 4 and Fig. 3B).

amygdala, and right pallidum compared with male patients and healthy controls (Table 3 and Fig. 2B and Supplementary Table 2, available online as Supplemental Digital Content at http://links.lww.com/PAIN/A125).

3.3. Impact of development on migraine

3.2.3. Functional findings

3.3.1. Structural findings

To assess rsFC differences between patients and healthy controls, a data-driven approach was used. Accordingly, rsFC was performed for the amygdala and PCu, as these brain regions (1) yielded structural GM differences (see structural findings) and (2) were found to have significant sex differences in adult migraineurs.34 No subject was excluded due to excessive motion (ie, .3 mm). The average motion 6 SEM for patients was 0.30 6 0.03 mm, and the average motion for healthy controls was 0.32 6 0.05 mm. An independent samples t test revealed that there is no significant difference in motion between patients and controls (t(54) 5 0.33, P 5 0.74). Hence, our findings revealed that females with migraine exhibited greater rsFC between the right PCu and the left putamen, right caudate, left thalamus, and left amygdala compared with males with migraine and healthy controls (ie, significant sex-by-disease interaction) (Table 4 and Fig. 3A and Supplementary Table 3, available online as Supplemental Digital Content at http://links.lww.com/PAIN/A125). Moreover, intriguingly, female patients also showed greater rsFC between the left

To evaluate the impact of development in migraine sex differences, we compared males and females with migraine with healthy children during different developmental stages, ie, early puberty (ie, 10-11 years) vs midpuberty (ie, 14-16 years), separately. Females with migraine at an early stage of puberty showed significant cortical thickening in the right M1 and right aMCC when compared with early puberty male migraineurs and healthy controls (Table 5 and Fig. 4A). However, males with migraine displayed a significant cortical thinning in the left aMCC and left medial prefrontal cortex (mPFC) when compared with early puberty female migraineurs and healthy controls (Table 5 and Fig. 4A). During midpuberty, female patients displayed cortical thickening in the left S1 and left M1 when compared with midpuberty male patients and healthy control children (Table 5 and Fig. 4A). Our VBM analysis revealed that, when contrasting early puberty sex differences in children with migraine, female patients

Table 4

Precuneus and amygdala rsFC in females and males with migraine and healthy controls. Contrasts/cortical brain regions Functional connectivity—R PCu Females (Mg . Hc) . males (Mg . Hc) L putamen R caudate L thalamus L amygdala Males (Mg . Hc) . females (Mg . Hc) NS Functional connectivity—L amygdala Females (Mg . Hc) . males (Mg . Hc) L thalamus R thalamus L aMCC R SMA R aMCC Males (Mg . Hc) . females (Mg . Hc) NS

MNI coordinates x

y

z

216 12 212 218

8 8 212 24

0 16 24 28

26 18 26 18 8

222 218 0 22 22

2 2 42 68 44

No. of voxels

t score

690

3.52 3.30 2.97 2.93

1218

3.74 3.63 3.22 3.11 3.00

* * *

† 859 ‡ ‡

* Subcluster of 216, 8, 0. † Subcluster of 26, 222, 2. ‡ Subcluster of 26, 0, 42. aMCC, anterior midcingulate cortex; Hc, healthy controls; L, left; Mg, migraineurs; NS, not significant; PCu, precuneus; R, right; rsFC, resting state functional connectivity; SMA, supplementary motor area.

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females with migraine had more GM in the right thalamus, bilateral putamen, bilateral amygdala and left caudate than males with migraine and healthy children (Table 6 and Fig. 4B). 3.3.2. Functional findings Based on the previously described sex-related midpuberty cortical and volumetric differences, rsFC was performed for bilateral amygdalar seeds. However, there were no significant differences when contrasting males and females with migraine against sex- and age-matched healthy children during early or later developmental stage. 3.3.3. Summary of results Our primary analysis aimed to define migraine-related changes across sex to determine whether sex differences that have been previously observed in adult migraineurs34 are already present in pediatric migraineurs. In this study, we found that female patients had more GM in the S1, SMA, PCu, caudate, pallidum, and amygdala, as well as greater amygdala rsFC to the thalamus, aMCC, and SMA, compared with male patients. Moreover, females had greater PCu rsFC to the caudate, putamen, thalamus, and amygdala than males. Our secondary analysis evaluated the impact of development (ie, earlier stage of puberty at 10-11 years vs later stage of puberty at 14-16 years) in migraine sex differences. At early puberty, males with migraine had more GM in the aMCC and mPFC compared with females, whereas females exhibited more GM in M1, aMCC, putamen, thalamus, and hippocampus compared with males. Finally, at midpuberty, females exhibited more GM in the S1, M1, caudate, putamen, thalamus, and amygdala compared with males.

Figure 3. Sex-related resting state functional connectivity (rsFC) changes between patients with migraine (Mg) and healthy controls (Hc). (A) Females with migraine (shown in pink) had greater rsFC between the right precuneus and the left putamen (Put), right caudate (Cau), left thalamus (Thal), and left amygdala (Amy) compared with males with migraine and healthy controls. (B) Females with migraine (shown in pink) had greater rsFC between the left amygdala and the bilateral thalamus (Thal) extending into left insula (Ins), right supplementary motor area, and bilateral anterior midcingulate cortex compared with males with migraine and healthy controls.

4. Discussion This is the first study investigating structural and functional brain differences in girls and boys with a history of migraine compared with age- and sex-matched healthy controls. 4.1. Sex differences in pediatric migraine

had more GM in the left putamen, bilateral thalamus, and left hippocampus than male patients and healthy controls (Table 6 and Fig. 4B). Sex-related midpuberty volume comparison showed that

Contrary to previous results observed in adults,34 we did not find any significant differences between males and females in their

Table 5

Cortical GM thickness in females and males with migraine and healthy controls at early puberty and midpuberty. Contrasts/cortical brain regions

MNI coordinates x

Early puberty: (females: Mg . Hc) . (males: Mg . Hc) R primary motor cortex R aMCC Early puberty: (males: Mg . Hc) . (females: Mg . Hc) L aMCC L mPFC Midpuberty: (females: Mg . Hc) . (males: Mg . Hc) L primary somatosensory cortex L primary motor cortex Midpuberty: (males: Mg . Hc) . (females: Mg . Hc) NS

y

No. of vertices

t score

z

39 8

24 11

61 27

107 74

2.90 2.87

25 222

25 58

19 8

140 86

3.84 4.79

262 254

210 24

28 18

120 82

3.61 3.25

aMCC, anterior midcingulate cortex; GM, gray matter; Hc, healthy controls; L, left; Mg, migraineurs; mPFC, medial prefrontal cortex; NS, not significant; R, right.

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Figure 4. Sex-related structural brain differences between patients with migraine (Mg) and healthy controls (Hc) during early puberty and midpuberty. (A) At early puberty, females with migraine (shown in pink) had cortical thickening in the right primary motor cortex (M1) and right anterior midcingulate cortex compared with early puberty migraine males and healthy controls. Contrary, males with migraine (shown in green) showed significant cortical thinning in the left anterior midcingulate cortex and left medial prefrontal cortex compared with early puberty females with migraine and healthy controls. (B) Females with migraine (shown in pink) had more gray matter in the left putamen (Put), bilateral thalamus (Thal), and left hippocampus (Hip) compared with males with migraine and healthy children. (A) At midpuberty, females with migraine (shown in pink) had cortical thickening in the left primary somatosensory cortex (S1) and left primary motor cortex (M1) compared with midpuberty males with migraine and healthy children. (B) Females with migraine (shown in pink) had had more gray matter in the right thalamus (Thal), bilateral putamen (Put), bilateral amygdala (Amyg), and left caudate (Cau) compared with males with migraine and healthy children.

time with migraine, migraine frequency, and pain unpleasantness. Nevertheless, in this study, females showed a tendency towards greater migraine duration and higher pain intensity compared with males. Intriguingly, female patients also had a significant GM increase in sensory regions such as S1 compared with male patients, a finding that could represent a susceptibility to repeated nociceptive drive.31 Moreover, significant overlaps were found in sex-related structural brain alterations in children and adults.34 In this study, the PCu was significantly thicker in females compared with males, as previously noted in adult females.34 The PCu is involved in a number of brain functions related to sensorimotor processing, cognition, and visual processing.12 Because of its strategic connections, and its involvement in global integration of information, the PCu may be a key region underlying migraine sex differences.34 Cortical thickening may be driven by hormones such as estrogens that may influence the development or functioning of

sensory processing in this region48,55; however, the impact of sex hormones on brain structure needs further study. In addition to cortical changes, females also showed significant increases in GM volume in subcortical regions such as the caudate and pallidum. Remarkably, the basal ganglia (BG) have shown both functional and structural differences in adult migraineurs,23,33 but have not yet been defined across sex in migraine. The BG are known to play an important part in pain processing.7 Of note, sexual dimorphism has been previously described in BG volumes.42 For example, the mean volumes in the caudate (females . males) and pallidum (males . females) were shown to differentiate children aged 4 to 18 years.21 Here, we report increased volume in the caudate and pallidum in females with migraine as compared with males with migraine when controlling for sex (ie, healthy controls), suggesting that sexual dimorphism may be exacerbated in these regions in the migraine state.

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Table 6

Subcortical GM volume in females and males with migraine and healthy controls at early puberty and midpuberty. Contrasts/subcortical brain regions Early puberty: (females: Mg . Hc) . (males: Mg . Hc) L putamen R thalamus L hippocampus L thalamus Early puberty: (males: Mg . Hc) . (females: Mg . Hc) NS Midpuberty: (females: Mg . Hc) . (males: Mg . Hc) R thalamus R putamen L amygdala R amygdala L putamen L caudate Midpuberty: (males: Mg . Hc) . (females: Mg . Hc) NS

No. of voxels

t score

22 22 26 2

536 161 54 42

3.93 2.18 2.36 2.50

16 14 228 216 14 22

478 404 359 326 176 74

2.80 3.56 2.93 2.74 3.46 2.83

MNI coordinates x

y

224 6 232 214

18 210 234 220

10 28 226 32 224 218

216 210 0 22 28 28

z

GM, gray matter; Hc, healthy controls; L, left; Mg, migraineurs; NS, not significant; R, right.

Another subcortical region altered with sex in migraine was the amygdala. The amygdala, known as the “fear hub,” has also been implicated in pain processes.46 Furthermore, sex differences in amygdala responses are also well known.24 In our study in adults with migraine,34 we have previously reported a greater involvement of the amygdala in adult female migraineurs as compared with adult male migraineurs during noxious thermal stimulation. The present observation of greater amygdala volume in migraine females may relate to the fact that females are twice as vulnerable as males in processing fear and developing anxiety or depression.3,4 Importantly, studies have shown that fear and anxiety play a significant role in the transition from acute to chronic pain,25 and females have an increased risk of transitioning from episodic to chronic migraine.19 Estrogen rapidly alters activation of amygdala neurons,39 which may influence fear and pain behaviors when given systemically.20 Although the underlying mechanisms remain unknown, our rsFC results revealed a significant sexual dimorphism for the left amygdala to insula, aMCC, and thalamus. These rsFC increases are of great interest, as enhanced rsFC between the amygdala and insula is thought to be involved in visceroceptive processing in adult migraineurs.23 Alterations in rsFC between the amygdala and BG have also been previously documented in nonmigraine conditions.41 Interestingly, the laterality of these changes has been noted in the left amygdala for other pain conditions in children such as complex regional pain syndrome.47 Additionally, the involvement of the left amygdala in emotional stimuli and processing seems to be prominent in women.10 Taken together, the reported changes are similar to those observed in female vs male adult migraineurs for some (viz., PCu) but not all (viz., insula) brain areas.34 Differences between pediatric and adult migraine may thus relate to other factors such as the duration of migraine44 or cumulative effects of repeated medications. 4.2. Impact of development on migraine While investigating the impact of development on migraine differences between males and females, results revealed sex

disparities in early puberty and midpuberty. During early puberty, females with migraine had increased cortical thickness in M1 and aMCC (in the right hemisphere) and increased GM volume in the putamen, thalamus, and hippocampus. Male patients however had thicker mPFC and aMCC (in the left hemisphere) compared with female patients during early puberty, suggesting that there may be preexisting cortical and subcortical migraine differences between sexes that are unrelated to puberty or development. Interestingly, however, although some of these differential migraine changes seem to resolve along puberty, especially in males (ie, aMCC and mPFC), others persist in females (ie, M1, putamen, and thalamus). Moreover, at midpuberty, females with migraine showed increased GM in S1, amygdala, and caudate compared with males with migraine and matched healthy controls. Our data therefore support the hypothesis that hormonal changes may significantly impact migraine. The observed sex-related neural differences around midpuberty may underlie the sex disparity evident in migraine prevalence around midpuberty, the increased female risk of transition from episodic into chronic migraine, and the increased comorbidity with depression reported in females.19 4.3. Brain system insights into resistance and resilience of migraine The nature of the changes associated with sex differences suggests that certain brain areas are either more affected by the disease or potentially part of the migraine brain phenotype. Across the sexes in children, the differences include S1, PCu, SMA, caudate, putamen, thalamus, and amygdala. In adults, sex-related differences include the PCu, insula, and amygdala. Thus, there may be a transition of regional differences during brain development, and, additionally, sex differences may confer decreased resistance to migraine. These alterations in GM correlate with altered function. For example, alterations in GM18 in chronic pain states may result in altered rsFC in brain regions associated with pain modulation processes, which may “normalize” with successful treatment.2,18 Thus, alterations in specific

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brain regions may constitute a marker for behavioral phenotypes, similar in fashion to substantia nigra alterations observed in Parkinson’s disease.27 Alternatively, stress may innately drive the migraine condition, which can alter brain structure and functional connectivity.6,37 Taken together, changes in brain structures may thus lead to a brain state that is resilient or vulnerable to migraine propensity and attacks. The added changes induced by alterations in the hormonal milieu (viz., estrogen) may contribute to this allostatic load, resulting in brain structure and function alterations.49

Health (Grant Numbers: K24NS064050, R01NS0750182 to D. B.), the National Institutes of Health (Grant Number: R37 NS079678 to R.B.), the Mayday Fund/Louis Herlands Endowment for Pain Systems Neuroscience, and the Ryochi Sasakawa Young Leaders Fellowship Fund (SYLFF to V.F.).

Acknowledgements V. Faria and N. Erpelding are equally contributing authors.

Appendix A. Supplemental Digital Content 4.4. Study limitations There are a number of limitations in this study: (1) Group size for developmental analysis: although the total number of children enrolled was large (n 5 56), our analysis contrasting distinct developmental stages included only 7 children per group. Importantly, however, our findings were still significant after correction for multiple comparisons; (2) inclusion of migraineurs with and without aura: adult studies have shown distinct neural patterns between subtypes of migraine, but there are no imaging studies in pediatric migraine populations. Moreover, the number of patients with and without aura is almost evenly distributed, and our results should therefore be independent of migraine subtypes; (3) measures of puberty: we did not directly measure puberty in this study (standardized clinical measures,35,36,40,54 but segregated groups according to children’s age and normative age of puberty); (4) medications: some patients were taking abortive and preventive medications that can be a potential confounding factor for neural changes.43 Abortive (eg, triptans) and preventive (eg, amitriptyline) medications may alter brain circuits based on binding in the BG with triptans, but this has not been shown in a meticulous manner26,30; and (5) movement artifacts: imaging studies have shown that head motion can significantly affect rsFC measures.50 As a precaution, we used motion correction and ensured that motion in EPI scans was ,3 mm.

5. Conclusions This is the first study to evaluate sex differences in pediatric migraineurs, addressing the influence of development. While there are some important limitations, the data suggest significant differences in males and females. Females with migraine had significant GM increases in the S1, SMA, PCu, caudate, amygdala, and pallidum compared with males with migraine and healthy controls. Furthermore, during midpuberty, females exhibited significantly more GM in the S1, caudate, and amygdala compared with males during midpuberty and healthy controls. Overall, these results provide some initial insight into sex-related susceptibility and/or resilience to migraine attacks after puberty. These findings constitute a first step towards understanding differences in therapeutic approaches at a nascent stage of migraine-related changes in the brain, before possible migraine chronification. Measures of longitudinal changes involving brain structure and function across puberty in pediatric migraineurs will be necessary to further elucidate the brain plasticity in a condition that predominantly affects the female sex.

Conflict of interest statement The authors have no conflicts of interest to declare. This work was supported by the National Institute of Neurological Disorders and Stroke at the National Institutes of

Supplemental Digital Content associated with this article can be found online at http://links.lww.com/PAIN/A125. Article history: Received 27 January 2015 Received in revised form 13 June 2015 Accepted 2 July 2015 Available online 13 July 2015

References [1] Bartley EJ, Fillingim RB. Sex differences in pain: a brief review of clinical and experimental findings. Br J Anaesth 2013;111:52–8. [2] Becerra L, Sava S, Simons LE, Drosos A, Sethna N, Berde C, Lebel A, Borsook D. Intrinsic brain networks normalize with treatment in pediatric complex regional pain syndrome. Neuroimage Clinical 2014;6:347–69. [3] Beesdo K, Knappe S, Pine DS. Anxiety and anxiety disorders in children and adolescents: developmental issues and implications for DSM-V. Psychiatr Clin North Am 2009;32:483–524. [4] Born L, Shea A, Steiner M. The roots of depression in adolescent girls: is menarche the key? Curr Psychiatry Rep 2002;4:449–60. [5] Borsook D, Erpelding N, Lebel A, Linnman C, Veggeberg R, Grant PE, Buettner C, Becerra L, Burstein R. Sex and the migraine brain. Neurobiol Dis 2014;68:200–14. [6] Borsook D, Maleki N, Becerra L, McEwen B. Understanding migraine through the lens of maladaptive stress responses: a model disease of allostatic load. Neuron 2012;73:219–34. [7] Borsook D, Upadhyay J, Chudler EH, Becerra L. A key role of the basal ganglia in pain and analgesia–insights gained through human functional imaging. Mol Pain 2010;6:27. [8] Bramen JE, Hranilovich JA, Dahl RE, Forbes EE, Chen J, Toga AW, Dinov ID, Worthman CM, Sowell ER. Puberty influences medial temporal lobe and cortical gray matter maturation differently in boys than girls matched for sexual maturity. Cereb Cortex 2011;21:636–46. [9] Buse DC, Rupnow MF, Lipton RB. Assessing and managing all aspects of migraine: migraine attacks, migraine-related functional impairment, common comorbidities, and quality of life. Mayo Clin Proc 2009;84:422–35. [10] Cahill L. Why sex matters for neuroscience. Nat Rev Neurosci 2006;7: 477–84. [11] Carlson RV, Boyd KM, Webb DJ. The revision of the Declaration of Helsinki: past, present and future. Br J Clin Pharmacol 2004;57:695–713. [12] Cavanna AE, Trimble MR. The precuneus: a review of its functional anatomy and behavioural correlates. Brain 2006;129:564–83. [13] Chai NC, Peterlin BL, Calhoun AH. Migraine and estrogen. Curr Opin Neurol 2014;27:315–24. [14] Charlton E. Ethical guidelines for pain research in humans. Committee on Ethical Issues of the International Association for the Study of Pain. PAIN 1995;63:277–8. [15] Denuelle M, Fabre N. Functional neuroimaging of migraine. Rev Neurol (Paris) 2013;169:380–9. [16] Douaud G, Smith S, Jenkinson M, Behrens T, Johansen-Berg H, Vickers J, James S, Voets N, Watkins K, Matthews PM, James A. Anatomically related grey and white matter abnormalities in adolescent-onset schizophrenia. Brain 2007;130:2375–86. [17] Eising E, Datson AN, van den Maagdenberg AM, Ferrari MD. Epigenetic mechanisms in migraine: a promising avenue? BMC Med 2013;11:26. [18] Erpelding N, Simons LE, Lebel A, Serrano P, Pielech M, Prabhu S, Becerra L, Borsook D. Rapid treatment-induced brain changes in pediatric CRPS. Brain Struct Funct. 2014 Dec 17. [Epub ahead of print]. [19] Finocchi C, Strada L. Sex-related differences in migraine. Neurol Sci 2014;35(suppl 1):207–13.

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[20] Frye CA, Walf AA. Estrogen and/or progesterone administered systemically or to the amygdala can have anxiety-, fear-, and painreducing effects in ovariectomized rats. Behav Neurosci 2004;118: 306–13. [21] Giedd JN, Castellanos FX, Rajapakse JC, Vaituzis AC, Rapoport JL. Sexual dimorphism of the developing human brain. Prog Neuropsychopharmacol Biol Psychiatry 1997;21:1185–201. [22] Gupta S, McCarson KE, Welch KM, Berman NE. Mechanisms of pain modulation by sex hormones in migraine. Headache 2011;51:905–22. [23] Hadjikhani N, Ward N, Boshyan J, Napadow V, Maeda Y, Truini A, Caramia F, Tinelli E, Mainero C. The missing link: enhanced functional connectivity between amygdala and visceroceptive cortex in migraine. Cephalalgia 2013;33:1264–8. [24] Hamann S. Sex differences in the responses of the human amygdala. Neuroscientist 2005;11:288–93. [25] Hasenbring MI, Chehadi O, Titze C, Kreddig N. Fear and anxiety in the transition from acute to chronic pain: there is evidence for endurance besides avoidance. Pain Manag 2014;4:363–74. [26] Kacperski J, Hershey AD. Preventive drugs in childhood and adolescent migraine. Curr Pain Headache Rep 2014;18:422. [27] Lehericy S, Bardinet E, Poupon C, Vidailhet M, Francois C. 7 tesla magnetic resonance imaging: a closer look at substantia nigra anatomy in Parkinson’s disease. Mov Disord 2014;13:1574–81. [28] Lipton RB, Buse DC, Serrano D, Holland S, Reed ML. Examination of unmet treatment needs among persons with episodic migraine: results of the American Migraine Prevalence and Prevention (AMPP) Study. Headache 2013;53:1300–11. [29] Liu J, Qin W, Nan J, Li J, Yuan K, Zhao L, Zeng F, Sun J, Yu D, Dong M, Liu P, von Deneen KM, Gong Q, Liang F, Tian J. Gender-related differences in the dysfunctional resting networks of migraine suffers. PLoS One 2011;6: e27049. [30] Lopez-Alemany M, Ferrer-Tuset C, Bernacer-Alpera B. Akathisia and acute dystonia induced by sumatriptan. J Neurol 1997;244:131–2. [31] Maleki N, Becerra L, Brawn J, Bigal M, Burstein R, Borsook D. Concurrent functional and structural cortical alterations in migraine. Cephalalgia 2012;32:607–20. [32] Maleki N, Becerra L, Brawn J, McEwen B, Burstein R, Borsook D. Common hippocampal structural and functional changes in migraine. Brain Struct Funct 2013;218:903–12. [33] Maleki N, Becerra L, Nutile L, Pendse G, Brawn J, Bigal M, Burstein R, Borsook D. Migraine attacks the Basal Ganglia. Mol Pain 2011;7:71. [34] Maleki N, Linnman C, Brawn J, Burstein R, Becerra L, Borsook D. Her versus his migraine: multiple sex differences in brain function and structure. Brain 2012;135:2546–59. [35] Marshall WA, Tanner JM. Variations in pattern of pubertal changes in girls. Arch Dis Child 1969;44:291–303. [36] Marshall WA, Tanner JM. Variations in the pattern of pubertal changes in boys. Arch Dis Child 1970;45:13–23. [37] McEwen BS. The ever-changing brain: cellular and molecular mechanisms for the effects of stressful experiences. Dev Neurobiol 2012;72:878–90. [38] Merikangas KR. Contributions of epidemiology to our understanding of migraine. Headache 2013;53:230–46.

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[39] Nabekura J, Oomura Y, Minami T, Mizuno Y, Fukuda A. Mechanism of the rapid effect of 17 beta-estradiol on medial amygdala neurons. Science 1986;233:226–8. [40] Petersen AC, Crockett L, Richards M, Boxer A. A self-report measure of pubertal status: reliability, validity, and initial norms. J Youth Adolesc 1988;17:117–33. [41] Postuma RB, Dagher A. Basal ganglia functional connectivity based on a meta-analysis of 126 positron emission tomography and functional magnetic resonance imaging publications. Cereb Cortex 2006;16:1508–21. [42] Rijpkema M, Everaerd D, van der Pol C, Franke B, Tendolkar I, Fernandez G. Normal sexual dimorphism in the human basal ganglia. Hum Brain Mapp 2012;33:1246–52. [43] Rizzoli P. Preventive pharmacotherapy in migraine. Headache 2014;54: 364–9. [44] Schmitz N, Admiraal-Behloul F, Arkink EB, Kruit MC, Schoonman GG, Ferrari MD, van Buchem MA. Attack frequency and disease duration as indicators for brain damage in migraine. Headache 2008;48:1044–55. [45] Schulz KM, Sisk CL. Pubertal hormones, the adolescent brain, and the maturation of social behaviors: Lessons from the Syrian hamster. Mol Cell Endocrinol 2006;254-255:120–6. [46] Simons LE, Moulton EA, Linnman C, Carpino E, Becerra L, Borsook D. The human amygdala and pain: evidence from neuroimaging. Hum Brain Mapp 2014;35:527–38. [47] Simons LE, Pielech M, Erpelding N, Linnman C, Moulton E, Sava S, Lebel A, Serrano P, Sethna N, Berde C, Becerra L, Borsook D. The responsive amygdala: treatment-induced alterations in functional connectivity in pediatric complex regional pain syndrome. PAIN 2014;155:1727–42. [48] Smith JM, James MF, Bockhorst KH, Smith MI, Bradley DP, Papadakis NG, Carpenter TA, Parsons AA, Leslie RA, Hall LD, Huang CL. Investigation of feline brain anatomy for the detection of cortical spreading depression with magnetic resonance imaging. J Anat 2001; 198:537–54. [49] Spencer-Segal JL, Tsuda MC, Mattei L, Waters EM, Romeo RD, Milner TA, McEwen BS, Ogawa S. Estradiol acts via estrogen receptors alpha and beta on pathways important for synaptic plasticity in the mouse hippocampal formation. Neuroscience 2012;202:131–46. [50] Spisak T, Jakab A, Kis SA, Opposits G, Aranyi C, Berenyi E, Emri M. Voxel-wise motion artifacts in population-level whole-brain connectivity analysis of resting-state FMRI. PLoS One 2014;9:e104947. [51] Sprenger T, Borsook D. Migraine changes the brain: neuroimaging makes its mark. Curr Opin Neurol 2012;25:252–62. [52] Stewart WF, Roy J, Lipton RB. Migraine prevalence, socioeconomic status, and social causation. Neurology 2013;81:948–55. [53] Stewart WF, Wood C, Reed ML, Roy J, Lipton RB, Group AA. Cumulative lifetime migraine incidence in women and men. Cephalalgia 2008;28: 1170–8. [54] Teepker M, Peters M, Vedder H, Schepelmann K, Lautenbacher S. Menstrual variation in experimental pain: correlation with gonadal hormones. Neuropsychobiology 2010;61:131–40. [55] Zsarnovszky A, Belcher SM. Identification of a developmental gradient of estrogen receptor expression and cellular localization in the developing and adult female rat primary somatosensory cortex. Brain Res Dev Brain Res 2001;129:39–46.

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